To enable a resident to go home quietly without operating an intercom slave machine when he or she reaches home by alarm equipment performing alarm operation reliably to an obviously suspicious individual without making false operation.

A call button 12 of the intercom slave machine 1 is provided with a fingerprint sensor 13 for authenticating a visitor, has a database 12 for holding data for authentication, and a visitor determining device 3 for comparing fingerprint information transmitted by the fingerprint sensor 13 with fingerprint data stored in the database 12 to determine which of the three the visitor is, a safe person, a dangerous person, and an unknown person. On the basis of the determination result of the visitor determination device 3, an intercom master machine 2 performs lock control over an electric lock 5a.